The New Standard Part command enables you to insert another copy of the selected part.

You can find this command in the context menu that displays when right-clicking on a part inserted in the assembly.

If you select just one component, then right-click, the command works exactly as the Import command. Please refer to this document for more information.

If, however, you select more than one component before executing New Standard Part, the last component selected will be assumed to be the reference, and all selected parts will be substituted with this last one.